Commercial food mixers are frequently of a planetary-type having a stationary, mounted cylindrical bowl and a rotating beater which moves in orbital fashion within the bowl. There are generally two types of planetary gear systems used in mixers. Conventional planetary gears lack a central sun gear, and usually do not have space restriction concerns. The other type of planetary gear system utilizes a central sun-gear. Such a gear system requires less parts, has a higher speed reduction, and is more cost effective. However, the gear system utilizing a sun gear may have space restriction problems when adapted to fit in smaller mixers, such as a 10 quart mixer.
Mixers utilizing a central, sun gear typically includes a driven center shaft (sun shaft) and an agitator shaft orbiting around the center shaft. Both the center shaft and agitator shaft are housed in one or more bearing sets to guide their rotation. The bearing sets effectively increase the width of each shaft. In larger mixers, radial space is readily available, and thus bearings of various sizes may be used without concern for arrangement of the bearings. However, in smaller mixers, such as 10 quart mixers, space becomes more limited.
For smaller mixers, the distance between the agitator shaft and center shaft is restricted such that it is difficult to accommodate bearings therebetween. To resolve this problem, plain bearings have been used. However, plain bearings are not as reliable as ball or roller bearings due to the heavy load carried by the bearings, and due to the less effective lubrication provided by plain bearings. Alternatively, the problem has also been addressed by increasing the distance between the agitator shaft and the center shaft. However, this alteration necessitates several additional changes in the mixer design, including increasing the bowl diameter and modifying the bowl support, which increases the cost of such a mixer.
Accordingly, there exists a need for a planetary gear system for a mixer having a bearing arrangement wherein the agitator shaft and the central shaft may be located within close proximity of each other, and which is of relatively inexpensive and simple construction.